private Expression VisitStrMethodCall_ToString(MethodCallExpression m, ExpressionVisitorBase visitor)
{
visitor.Append("CAST(");
visitor.Visit(m.Object != null ? m.Object : m.Arguments[0]);
visitor.Append(" AS VARCHAR)");
return(m);
}
private Expression VisitStrMember_Length(MemberExpression m, ExpressionVisitorBase visitor)
{
visitor.Append("LEN(");
visitor.Visit(m.Expression);
visitor.Append(")");
return(m);
}
private Expression VisitStrMethodCall_Trim(MethodCallExpression m, ExpressionVisitorBase visitor)
{
if (m != null)
{
visitor.Append("RTRIM(LTRIM(");
visitor.Visit(m.Object != null ? m.Object : m.Arguments[0]);
visitor.Append("))");
}
return(m);
}
/// <summary>
/// 访问表示 null 合并运算的节点 a ?? b
/// </summary>
/// <param name="b">二元表达式节点</param>
/// <param name="visitor">访问器</param>
/// <returns></returns>
public override Expression VisitCoalesce(BinaryExpression b, ExpressionVisitorBase visitor)
{
// expression like a.Name ?? "TAN" => ISNULL(a.Name,'TAN')
visitor.Append("ISNULL(");
visitor.Visit(b.Left is ConstantExpression ? b.Right : b.Left);
visitor.Append(",");
visitor.Visit(b.Left is ConstantExpression ? b.Left : b.Right);
visitor.Append(")");
return(b);
}
private Expression VisitEnumMethodCall_Contains(MethodCallExpression m, ExpressionVisitorBase visitor)
{
if (m == null)
{
return(m);
}
MemberExpression member = m.Arguments[m.Arguments.Count - 1] as MemberExpression;
visitor.Visit(m.Arguments[m.Arguments.Count - 1]);
visitor.Append(" IN(");
//ConstantExpression constExpr = (m.Object != null ? m.Object : m.Arguments[0]) as ConstantExpression;
//visitor.Visit(constExpr);
Expression exp = m.Object != null ? m.Object : m.Arguments[0];
if (exp.NodeType == ExpressionType.Constant)
{
visitor.Visit(exp);
}
else if (exp.NodeType == ExpressionType.MemberAccess)
{
visitor.Visit(exp.Evaluate());
}
else if (exp.NodeType == ExpressionType.NewArrayInit)
{
var expressions = (exp as NewArrayExpression).Expressions;
for (int i = 0; i < expressions.Count; i++)
{
visitor.Visit(expressions[i]);
if (i < expressions.Count - 1)
{
visitor.Append(",");
}
}
}
visitor.Append(")");
return(m);
}
private Expression VisitStrMethodCall_SubString(MethodCallExpression m, ExpressionVisitorBase visitor)
{
if (m != null)
{
List <Expression> args = new List <Expression>(m.Arguments);
if (m.Object != null)
{
args.Insert(0, m.Object);
}
visitor.Append("SUBSTRING(");
visitor.Visit(args[0]);
visitor.Append(",");
visitor.Visit(args[1]);
visitor.Append(" + 1,");
if (args.Count == 3)
{
visitor.Visit(args[2]);
}
else
{
visitor.Append("LEN(");
visitor.Visit(args[0]);
visitor.Append(")");
}
visitor.Append(")");
}
return(m);
}
/// <summary>
/// 访问表示 null 判断运算的节点 a.Name == null
/// </summary>
/// <param name="b">二元表达式节点</param>
/// <param name="ExpressionVisitorBase">访问器</param>
/// <returns></returns>
public override Expression VisitEqualNull(BinaryExpression b, ExpressionVisitorBase visitor)
{
// a.Name == null => a.Name Is Null
string oper = b.NodeType == ExpressionType.Equal
? " IS "
: " IS NOT ";
visitor.Visit(b.Left is ConstantExpression ? b.Right : b.Left);
visitor.Append(oper);
visitor.Visit(b.Left is ConstantExpression ? b.Left : b.Right);
return(b);
}
private Expression VisitStrMethodCall_EndsWith(MethodCallExpression m, ExpressionVisitorBase visitor)
{
if (m != null)
{
visitor.Visit(m.Object);
visitor.Append(" LIKE ");
if (m.Arguments[0].NodeType == ExpressionType.Constant)
{
ConstantExpression c = m.Arguments[0] as ConstantExpression;
//visitor.Append(string.Format("N'%{0}'", c.Value));
visitor.Append("N'%");
visitor.Append(c.Value != null ? c.Value.ToString() : string.Empty);
visitor.Append("'");
}
else
{
visitor.Append("('%' + ");
visitor.Visit(m.Arguments[0]);
visitor.Append(")");
}
}
return(m);
}
