// +
public override DbExpression Visit(DbAddExpression exp)
{
MethodInfo method = exp.Method;
if (method != null)
{
Action<DbBinaryExpression, SqlGenerator> handler;
if (BinaryWithMethodHandlers.TryGetValue(method, out handler))
{
handler(exp, this);
return exp;
}
}
Stack<DbExpression> operands = GatherBinaryExpressionOperand(exp);
this.ConcatOperands(operands, " + ");
return exp;
}
static void StringConcat(DbBinaryExpression exp, SqlGenerator generator)
{
List <DbExpression> operands = new List <DbExpression>();
operands.Add(exp.Right);
DbExpression left = exp.Left;
DbAddExpression e = null;
while ((e = (left as DbAddExpression)) != null && (e.Method == UtilConstants.MethodInfo_String_Concat_String_String || e.Method == UtilConstants.MethodInfo_String_Concat_Object_Object))
{
operands.Add(e.Right);
left = e.Left;
}
operands.Add(left);
DbExpression whenExp = null;
List <DbExpression> operandExps = new List <DbExpression>(operands.Count);
for (int i = operands.Count - 1; i >= 0; i--)
{
DbExpression operand = operands[i];
DbExpression opBody = operand;
if (opBody.Type != UtilConstants.TypeOfString)
{
// 需要 cast type
opBody = DbExpression.Convert(opBody, UtilConstants.TypeOfString);
}
DbExpression equalNullExp = DbExpression.Equal(opBody, UtilConstants.DbConstant_Null_String);
if (whenExp == null)
{
whenExp = equalNullExp;
}
else
{
whenExp = DbExpression.And(whenExp, equalNullExp);
}
operandExps.Add(opBody);
}
generator._sqlBuilder.Append("CASE", " WHEN ");
whenExp.Accept(generator);
generator._sqlBuilder.Append(" THEN ");
DbConstantExpression.Null.Accept(generator);
generator._sqlBuilder.Append(" ELSE ");
generator._sqlBuilder.Append("(");
for (int i = 0; i < operandExps.Count; i++)
{
if (i > 0)
{
generator._sqlBuilder.Append(" + ");
}
generator._sqlBuilder.Append("ISNULL(");
operandExps[i].Accept(generator);
generator._sqlBuilder.Append(",");
DbConstantExpression.StringEmpty.Accept(generator);
generator._sqlBuilder.Append(")");
}
generator._sqlBuilder.Append(")");
generator._sqlBuilder.Append(" END");
}
// +
public override DbExpression Visit(DbAddExpression exp)
{
return(exp);
}
// +
public override DbExpression Visit(DbAddExpression exp)
{
return(exp.Accept(this._generator));
}
// + public abstract T Visit(DbAddExpression exp);
