chore: initial git load of code space
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Thom Lamb
@@ -0,0 +1,398 @@
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using System.Linq.Expressions;
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using System.Text;
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namespace Strata.SqlTools.Visitors.LinqToSql;
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/// <summary>
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/// Expression visitor for analyzing LINQ to SQL expression trees.
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/// Extracts query components such as SELECT, WHERE, JOIN, GROUP BY, and ORDER BY.
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/// </summary>
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public class LinqExpressionVisitor : ExpressionVisitor
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{
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private readonly StringBuilder _whereBuilder = new();
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private readonly StringBuilder _orderByBuilder = new();
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private readonly List<string> _methodCalls = new();
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private bool _isInWhereClause;
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#pragma warning disable IDE0052, S4487
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private bool _isInSelectClause;
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private bool _isInOrderByClause;
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private bool _isInGroupByClause;
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private string? _tableName;
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#pragma warning restore IDE0052, S4487
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/// <summary>
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/// Gets the SELECT clause extracted from the expression.
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/// </summary>
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public string? SelectClause { get; private set; }
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/// <summary>
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/// Gets the FROM clause (table name) extracted from the expression.
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/// </summary>
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public string? FromClause { get; private set; }
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/// <summary>
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/// Gets the WHERE clause extracted from the expression.
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/// </summary>
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public string? WhereClause { get; private set; }
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/// <summary>
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/// Gets the ORDER BY clause extracted from the expression.
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/// </summary>
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public string? OrderByClause { get; private set; }
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/// <summary>
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/// Gets the GROUP BY clause extracted from the expression.
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/// </summary>
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public string? GroupByClause { get; private set; }
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/// <summary>
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/// Gets the list of LINQ method calls in the query chain.
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/// </summary>
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public List<string> MethodCallChain => _methodCalls;
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/// <summary>
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/// Visits a method call expression.
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/// </summary>
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protected override Expression VisitMethodCall(MethodCallExpression node)
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{
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var methodName = node.Method.Name;
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_methodCalls.Add(methodName);
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switch (methodName)
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{
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case "Where":
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VisitWhereMethod(node);
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break;
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case "Select":
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VisitSelectMethod(node);
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break;
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case "OrderBy":
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case "OrderByDescending":
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case "ThenBy":
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case "ThenByDescending":
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VisitOrderByMethod(node);
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break;
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case "GroupBy":
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VisitGroupByMethod(node);
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break;
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case "Join":
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case "GroupJoin":
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VisitJoinMethod(node);
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break;
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case "Take":
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case "Skip":
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VisitTakeSkipMethod(node);
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break;
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default:
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// Visit the source expression
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Visit(node.Arguments[0]);
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break;
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}
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return node;
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}
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/// <summary>
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/// Visits a constant expression to extract the table name.
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/// </summary>
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protected override Expression VisitConstant(ConstantExpression node)
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{
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// Handle WHERE clause constants
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if (_isInWhereClause)
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{
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if (node.Value is string)
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{
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_whereBuilder.Append($"'{node.Value}'");
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}
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else if (node.Value != null)
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{
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_whereBuilder.Append(node.Value.ToString());
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}
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else
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{
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_whereBuilder.Append("NULL");
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}
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return node;
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}
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// Handle table name extraction
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if (node.Type.IsGenericType)
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{
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var genericType = node.Type.GetGenericTypeDefinition();
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if (genericType.Name.Contains("Table") || genericType.Name.Contains("Query"))
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{
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var entityType = node.Type.GetGenericArguments().FirstOrDefault();
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if (entityType != null)
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{
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_tableName = entityType.Name;
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FromClause = _tableName;
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}
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}
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}
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return base.VisitConstant(node);
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}
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private void VisitWhereMethod(MethodCallExpression node)
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{
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// Visit the source
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Visit(node.Arguments[0]);
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// Extract the predicate
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if (node.Arguments.Count > 1)
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{
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var lambda = StripQuotes(node.Arguments[1]) as LambdaExpression;
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if (lambda != null)
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{
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_isInWhereClause = true;
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Visit(lambda.Body);
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_isInWhereClause = false;
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if (_whereBuilder.Length > 0)
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{
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WhereClause = _whereBuilder.ToString();
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}
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}
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}
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}
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private void VisitSelectMethod(MethodCallExpression node)
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{
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// Visit the source
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Visit(node.Arguments[0]);
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// Extract the selector
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if (node.Arguments.Count > 1)
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{
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var lambda = StripQuotes(node.Arguments[1]) as LambdaExpression;
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if (lambda != null)
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{
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_isInSelectClause = true;
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var selectExpression = ExtractSelectExpression(lambda.Body);
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_isInSelectClause = false;
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if (!string.IsNullOrEmpty(selectExpression))
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{
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SelectClause = selectExpression;
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}
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}
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}
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}
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private void VisitOrderByMethod(MethodCallExpression node)
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{
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// Visit the source
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Visit(node.Arguments[0]);
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// Extract the key selector
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if (node.Arguments.Count > 1)
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{
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var lambda = StripQuotes(node.Arguments[1]) as LambdaExpression;
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if (lambda != null)
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{
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_isInOrderByClause = true;
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var orderByExpression = ExtractMemberName(lambda.Body);
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_isInOrderByClause = false;
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if (!string.IsNullOrEmpty(orderByExpression))
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{
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var direction = node.Method.Name.Contains("Descending") ? " DESC" : " ASC";
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if (_orderByBuilder.Length > 0)
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{
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_orderByBuilder.Append(", ");
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}
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_orderByBuilder.Append(orderByExpression + direction);
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OrderByClause = _orderByBuilder.ToString();
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}
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}
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}
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}
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private void VisitGroupByMethod(MethodCallExpression node)
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{
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// Visit the source
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Visit(node.Arguments[0]);
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// Extract the key selector
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if (node.Arguments.Count > 1)
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{
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var lambda = StripQuotes(node.Arguments[1]) as LambdaExpression;
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if (lambda != null)
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{
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_isInGroupByClause = true;
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var groupByExpression = ExtractMemberName(lambda.Body);
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_isInGroupByClause = false;
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if (!string.IsNullOrEmpty(groupByExpression))
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{
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GroupByClause = groupByExpression;
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}
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}
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}
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}
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private void VisitJoinMethod(MethodCallExpression node)
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{
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// Visit the source
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Visit(node.Arguments[0]);
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// For joins, we'd need more complex logic to extract full join information
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// This is a simplified version
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_methodCalls.Add($"{node.Method.Name} (complex join analysis not fully implemented)");
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}
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private void VisitTakeSkipMethod(MethodCallExpression node)
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{
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// Visit the source
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Visit(node.Arguments[0]);
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// Extract the count
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if (node.Arguments.Count > 1 && node.Arguments[1] is ConstantExpression constant)
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{
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_methodCalls.Add($"{node.Method.Name}({constant.Value})");
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}
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}
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/// <summary>
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/// Visits a binary expression (e.g., comparisons, logical operations).
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/// </summary>
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protected override Expression VisitBinary(BinaryExpression node)
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{
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if (_isInWhereClause)
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{
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_whereBuilder.Append("(");
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Visit(node.Left);
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_whereBuilder.Append($" {GetOperator(node.NodeType)} ");
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Visit(node.Right);
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_whereBuilder.Append(")");
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return node;
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}
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return base.VisitBinary(node);
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}
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/// <summary>
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/// Visits a member access expression.
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/// </summary>
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protected override Expression VisitMember(MemberExpression node)
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{
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if (_isInWhereClause)
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{
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var memberName = GetFullMemberName(node);
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_whereBuilder.Append(memberName);
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return node;
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}
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return base.VisitMember(node);
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}
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private string ExtractSelectExpression(Expression expression)
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{
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if (expression is NewExpression newExpr)
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{
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var members = new List<string>();
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for (int i = 0; i < newExpr.Arguments.Count; i++)
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{
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var memberName = ExtractMemberName(newExpr.Arguments[i]);
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var alias = newExpr.Members?[i].Name;
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if (!string.IsNullOrEmpty(alias) && alias != memberName)
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{
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members.Add($"{memberName} AS {alias}");
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}
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else
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{
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members.Add(memberName);
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}
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}
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return string.Join(", ", members);
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}
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var name = ExtractMemberName(expression);
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return string.IsNullOrEmpty(name) ? "*" : name;
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}
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private string ExtractMemberName(Expression expression)
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{
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if (expression is MemberExpression member)
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{
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return GetFullMemberName(member);
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}
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if (expression is ParameterExpression param)
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{
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return "*";
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}
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if (expression is MethodCallExpression methodCall)
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{
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return $"{methodCall.Method.Name}(...)";
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}
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return expression.ToString();
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}
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private string GetFullMemberName(MemberExpression expression)
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{
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var parts = new Stack<string>();
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var current = expression;
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while (current != null)
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{
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parts.Push(current.Member.Name);
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if (current.Expression is MemberExpression memberExpr)
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{
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current = memberExpr;
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}
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else if (current.Expression is ParameterExpression paramExpr)
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{
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// Use parameter name as table alias if it's not the default
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if (paramExpr.Name != null && paramExpr.Name.Length == 1)
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{
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parts.Push(paramExpr.Name);
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}
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break;
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}
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else
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{
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break;
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}
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}
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return string.Join(".", parts);
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}
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private string GetOperator(ExpressionType nodeType)
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{
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return nodeType switch
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{
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ExpressionType.Equal => "=",
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ExpressionType.NotEqual => "!=",
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ExpressionType.GreaterThan => ">",
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ExpressionType.GreaterThanOrEqual => ">=",
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ExpressionType.LessThan => "<",
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ExpressionType.LessThanOrEqual => "<=",
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ExpressionType.AndAlso => "AND",
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ExpressionType.OrElse => "OR",
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ExpressionType.Add => "+",
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ExpressionType.Subtract => "-",
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ExpressionType.Multiply => "*",
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ExpressionType.Divide => "/",
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_ => nodeType.ToString()
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};
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}
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private static Expression StripQuotes(Expression expression)
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{
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while (expression.NodeType == ExpressionType.Quote)
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{
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expression = ((UnaryExpression)expression).Operand;
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}
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return expression;
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}
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}
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