/// <summary>
/// 尝试将 exp 转换成 DbParameterExpression。
/// </summary>
/// <param name="exp"></param>
/// <returns></returns>
public static DbExpression ParseDbExpression(this DbExpression exp)
{
DbExpression stripedExp = DbExpressionHelper.StripInvalidConvert(exp);
DbExpression tempExp = stripedExp;
List <DbConvertExpression> cList = null;
while (tempExp.NodeType == DbExpressionType.Convert)
{
if (cList == null)
{
cList = new List <DbConvertExpression>();
}
DbConvertExpression c = (DbConvertExpression)tempExp;
cList.Add(c);
tempExp = c.Operand;
}
if (tempExp.NodeType == DbExpressionType.Constant || tempExp.NodeType == DbExpressionType.Parameter)
{
return(stripedExp);
}
if (tempExp.NodeType == DbExpressionType.MemberAccess)
{
DbMemberExpression dbMemberExp = (DbMemberExpression)tempExp;
if (ExistDateTime_NowOrDateTime_UtcNow(dbMemberExp))
{
return(stripedExp);
}
DbParameterExpression val;
if (DbExpressionExtensions.TryParseToParameterExpression(dbMemberExp, out val))
{
if (cList != null)
{
if (val.Value == DBNull.Value)//如果是 null，则不需要 Convert 了，在数据库里没意义
{
return(val);
}
DbConvertExpression c = null;
for (int i = cList.Count - 1; i > -1; i--)
{
DbConvertExpression item = cList[i];
c = new DbConvertExpression(item.Type, val);
}
return(c);
}
return(val);
}
}
return(stripedExp);
}
static void EnsureTrimCharArgumentIsSpaces(DbExpression exp)
{
var m = exp as DbMemberExpression;
if (m == null)
{
throw new NotSupportedException();
}
DbParameterExpression p;
if (!DbExpressionExtensions.TryParseToParameterExpression(m, out p))
{
throw new NotSupportedException();
}
var arg = p.Value;
if (arg == null)
{
throw new NotSupportedException();
}
var chars = arg as char[];
if (chars.Length != 1 || chars[0] != ' ')
{
throw new NotSupportedException();
}
}
public override DbExpression Visit(DbMemberExpression exp)
{
MemberInfo member = exp.Member;
if (member.DeclaringType == UtilConstants.TypeOfDateTime)
{
if (member == UtilConstants.PropertyInfo_DateTime_Now)
{
this._sqlBuilder.Append("DATETIME('NOW','LOCALTIME')");
return(exp);
}
if (member == UtilConstants.PropertyInfo_DateTime_UtcNow)
{
this._sqlBuilder.Append("DATETIME()");
return(exp);
}
if (member == UtilConstants.PropertyInfo_DateTime_Today || member == UtilConstants.PropertyInfo_DateTime_Date)
{
this._sqlBuilder.Append("DATE('NOW','LOCALTIME')");
return(exp);
}
if (IsDbFunction_DATEPART(exp))
{
return(exp);
}
}
DbParameterExpression newExp;
if (DbExpressionExtensions.TryParseToParameterExpression(exp, out newExp))
{
return(newExp.Accept(this));
}
if (member.Name == "Length" && member.DeclaringType == UtilConstants.TypeOfString)
{
this._sqlBuilder.Append("LENGTH(");
exp.Expression.Accept(this);
this._sqlBuilder.Append(")");
return(exp);
}
else if (member.Name == "Value" && Utils.IsNullable(exp.Expression.Type))
{
exp.Expression.Accept(this);
return(exp);
}
throw new NotSupportedException(string.Format("'{0}.{1}' is not supported.", member.DeclaringType.FullName, member.Name));
}
