这么写不能判断空值吗

这样写不能判断空值吗

C# code

        private void DataLoad()        {            string strQuery = "";            if (txtManagementId.Text.Trim() != "")            {                if (strQuery != "")                {                    strQuery = strQuery + " AND ";                }                strQuery = strQuery + " UserId LIKE '%" + txtManagementId.Text.Trim() + "%' ";            }            if (txtUserId.Text.Trim() != "")            {                if (strQuery != "")                {                    strQuery = strQuery + " AND ";                }                strQuery = strQuery + " UserNumber LIKE '%" + txtUserId.Text.Trim() + "%' ";            }            if (cboUserGrade.SelectedValue != "")            {                if (strQuery != "")                {                    strQuery = strQuery + " AND ";                }                strQuery = strQuery + " UserGrade = '" + cboUserGrade.SelectedValue + "' ";            }}

我定义了一个DateLoad要完成它的搜索功能

[解决办法]
if (strQuery != "")
{
strQuery = strQuery + " AND ";
}

不知楼主为什么要做个这判断，如果为空的话，那你后面的语句再执行会报错的