how to check emailid already exist while registering on textbox leave event when new user in winforms

Question

Answer 1

@Amita Kharat , Based on your description, you want to check if the EmailId already exists in the database when you register the information in the textbox leave event.

I suggest that you could use SqlReader.HasRows to check it.

Here is a code example you could refer to.

 private void txtEmailId_Leave(object sender, EventArgs e)  
        {  
            SqlConnection connection = new SqlConnection(connstr);  
            connection.Open();  
            string sql = string.Format("select * from EmailDetail where EmailId={0}", txtEmailId.Text);  
            SqlCommand command = new SqlCommand(sql,connection);  
            SqlDataReader reader = command.ExecuteReader();  
            if(reader.HasRows)  
            {  
                MessageBox.Show("The EmailId already exists in the database");  
            }  
            else  
            {  
                MessageBox.Show("The EmailId does not exist in the database");  
            }  
  
        }  

I created a simple table so that we can make a test.

The following is tested result:

Best Regards,
Jack

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