Validate field in mssql if has value or null

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C#

con1.Open();
SqlCommand cmd = new SqlCommand("Select first from TransactionsInfo where name=@name and tid=@tid", con1);
cmd.Parameters.AddWithValue("@name", txtName.Text);
cmd.Parameters.AddWithValue("@tid", txtId.Text);
SqlDataReader rdr = cmd.ExecuteReader();

if (!DBNull.Value.Equals(rdr["first"]))
{
    MessageBox.Show("First payment already exists in database .", "Alert !", MessageBoxButtons.OK, MessageBoxIcon.Error);
}
else
{
//save
}

I want to validate if my field "first" in TransactionsInfo table has value or null
ty in advance :)

Posted 29-May-14 16:56pm

Member 10717094

Updated 29-May-14 17:02pm

DamithSL

v2

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syed shanu 29-May-14 23:04pm

so what is the problem yiou can check null value in sql query itself
select ISNULL(first ,'') from TransactionsInfo where name=@name and tid=@tid

Member 10717094 29-May-14 23:07pm

do i have to use sqldatareader and what condition to use?
thanks for ur reply

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DamithSL · Accepted Answer · 2014-05-29T17:06:00

Solution 1

C#

//check for rows 
if (rdr.HasRows)
{            
    // for reading one row
    if (rdr.Read())
    {
        if(dr1["first"] != DBNull.Value)
       {
            MessageBox.Show("First payment already exists in database .", "Alert !", MessageBoxButtons.OK, MessageBoxIcon.Error); 
       }else
       {
          // dr1["first"] has DBNull
       }
    }
}else
{
   // no rows returned by the reader, show message....
}

Posted 29-May-14 17:06pm

DamithSL

Updated 29-May-14 17:11pm

v4

Comments

Member 10717094 29-May-14 23:17pm

thanks Damith it works fine

DamithSL 29-May-14 23:19pm

You are welcome!