如果条件为查询与空结果

Question

我写了这个SQL查询:

 SqlCommand cmd2 = new SqlCommand();
        cmd2.Connection = new SqlConnection(Class1.CnnStr);
        cmd2.CommandText = "SELECT MAX(Code) FROM Table WHERE Number=@Number ";
        cmd2.Connection.Open();
        cmd2.Parameters.AddWithValue("@Number", Hidden_txt.Text);
        cmd2.ExecuteNonQuery();

我想添加一些if条件,如:

if (cmd2.ExecuteScalar()=="Null")
{....}

如何在我的查询没有答案时添加if条件？

Answer 1

删除对cmd2.ExecuteNonQuery的调用,然后添加如下内容:

object maxCode = cmd2.ExecuteScalar();
if (maxCode == null)
{
    // Null
}
else
{
    // do something with maxCode, you probably want to cast - e.g. (int)maxCode
}