T-SQL中的位类型

Question

In my table, I use the bit type for IsTrue column.

When I execute the select command:

SqlDataReader reader = command.ExecuteReader(); 

I'm not sure that what would the reader["isTrue"] return ?

I tried doing the comparison

reader["isTrue"].ToString().Equals("0")

but it didn't work well. Can somebody tell me what I did incorrectly?

Answer 1

It returns a boolean value.

bool value = (bool)reader["IsTrue"];

If you know the index of the column in the result set, you can use:

bool value = reader.GetBoolean(index);

Answer 2

I like to do this with extension methods:

public static bool ToBool(this string theString)
    {
        bool result = false;
        bool.TryParse(theString, out result);
        return result;

    }

And in your code you can simply do this:

if(reader["isTrue"].ToBool())
{
}

The ToBool extension method will return true/false in the following cases:

• false if reader["isTrue"] returns DBNull.Value
• false if reader["isTrue"] returns 0 (as bit)
• true if reader["istrue"] returns 1 (as bit)

And it will never throw an exception when you execute it unless the "isTrue" column is not present in your result set, obviously.