public static string CreateQuery <TableType>(ParameterFactory parameterFactory, Expression <Func <TableType, bool> > expression) where TableType : DatabaseTable, new()
{
var visitor = new WhereExpressionVisitor <TableType>(parameterFactory);
visitor.Visit(expression);
var query = visitor.GetQuery();
return(query.HasValue()
? " WHERE " + query
: string.Empty);
}
public override Expression Visit(Expression node)
{
if (node is MethodCallExpression methodCallExpression && methodCallExpression.Method.Name == "Contains")
{
var argumentVisitor = new WhereExpressionVisitor <TableType>(new ParameterFactory());
argumentVisitor.Visit(methodCallExpression.Arguments);
var callVisitor = new WhereExpressionVisitor <TableType>(new ParameterFactory());
callVisitor.Visit(methodCallExpression.Object);
if (methodCallExpression.Method.DeclaringType == typeof(string))
{
stringBuilder.Append(callVisitor.stringBuilder);
stringBuilder.Append(" LIKE ");
stringBuilder.Append(parameterFactory.Create("%" + argumentVisitor.parameterFactory.parameters.Single().Value + "%"));
return(node);
}
else if (methodCallExpression.Method.DeclaringType.IsGenericType && typeof(IEnumerable).IsAssignableFrom(methodCallExpression.Method.DeclaringType))
{
stringBuilder.Append(argumentVisitor.stringBuilder);
stringBuilder.Append(" IN ");
stringBuilder.Append('(');
for (var i = 0; i < callVisitor.parameterFactory.parameters.Count; i++)
{
var parameter = callVisitor.parameterFactory.parameters[i];
var value = parameter.Value;
var valueExpression = parameterFactory.Create(value);
stringBuilder.Append(valueExpression);
if (i != callVisitor.parameterFactory.parameters.Count - 1)
{
stringBuilder.Append(',');
stringBuilder.Append(' ');
}
}
stringBuilder.Append(')');
return(node);
}
}
if (node is MemberExpression memberExpression && memberExpression.Expression.Type == typeof(TableType) && memberExpression.Expression.NodeType == ExpressionType.Parameter)
{
var columnExpression = "[" + memberExpression.Member.Name + "]";
stringBuilder.Append(columnExpression);
return(node);
}
if (node is MemberExpression m)
{
var objectMember = Expression.Convert(m, typeof(object));
var getterLambda = Expression.Lambda <Func <object> >(objectMember);
var getter = getterLambda.Compile();
var value = getter.Invoke();
var parameterizedValue = parameterFactory.Create(value);
stringBuilder.Append(parameterizedValue);
return(node);
}
if (node is ConstantExpression constantExpression)
{
if (constantExpression.Value == null)
{
stringBuilder.Append("NULL");
return(node);
}
else if (constantExpression.Value.GetType().IsClass == false || constantExpression.Value is string)
{
var value = constantExpression.Value;
var parameterizedValue = parameterFactory.Create(value);
stringBuilder.Append(parameterizedValue);
return(node);
}
else
{
var fields = constantExpression.Value.GetType().GetFields();
if (fields.Length != 1)
{
throw new NotSupportedException();
}
var field = fields.Single();
var value = field.GetValue(constantExpression.Value);
var parameterizedValue = parameterFactory.Create(value);
stringBuilder.Append(parameterizedValue);
return(node);
}
}
if (node is BinaryExpression binaryExpression)
{
var addParantheses = binaryExpression.NodeType.In(ExpressionType.AndAlso, ExpressionType.OrElse);
operatorStack.Push(node.NodeType);
if (addParantheses)
{
stringBuilder.Append('(');
}
Visit(binaryExpression.Left);
if (addParantheses)
{
stringBuilder.Append(')');
}
var operatorIndex = stringBuilder.Length;
var operatorPlaceholder = "{{" + Guid.NewGuid() + "}}";
stringBuilder.Append(operatorPlaceholder);
if (addParantheses)
{
stringBuilder.Append('(');
}
Visit(binaryExpression.Right);
if (addParantheses)
{
stringBuilder.Append(')');
}
var operatorExpression = GetOperatorExpression(node.NodeType, binaryExpression.Left, binaryExpression.Right);
stringBuilder.Replace(operatorPlaceholder, operatorExpression, operatorIndex, Guid.Empty.ToString().Length + "{{}}".Length);
operatorStack.Pop();
return(node);
}
return(base.Visit(node));
}
