Question

I want to update a database in my asp.net application. The updated fields are set in textboxs.

SqlCommand cmd = new SqlCommand();
cmd.Connection = con;

cmd.ExecuteNonQuery();
cmd.CommandText = "update dbo.User_Info SET FirstName=@FirstName, LastName=@LastName,Degree=@Degree,Organization=@Organization,Phone=@Phone,Ext=@Ext where UserName =@username";
cmd.Parameters.Add("FirstName", SqlDbType.VarChar).Value = TextFirstName.Text;
 cmd.Parameters.Add("LastName", SqlDbType.VarChar).Value = TextLastName.Text;
 cmd.Parameters.Add("Degree", SqlDbType.VarChar).Value = TextDegree.Text;
 cmd.Parameters.Add("Organization", SqlDbType.VarChar).Value = TextOrg.Text;
 cmd.Parameters.Add("Phone", SqlDbType.VarChar).Value = TextPhone.Text;
 cmd.Parameters.Add("Ext", SqlDbType.VarChar).Value = TextExt.Text;

However maybe some fields I don’t want to update them at all. Just leave them as blank, so how to modify the code?
For example, suppose I just want to update FirstName, the command should be

cmd.CommandText = "update dbo.User_Info SET FirstName=@FirstName where UserName =@username";

However another guy just want to update “Degree”, therefore the command will be:

cmd.CommandText = "update dbo.User_Info SET Degree=@Degree where UserName =@username";

Is there an universal command for considering various scenarios?

Answer 1

Universal? I doubt it. Some options:

Customize your UPDATE statements based on the inputs by dynamically adding the fields:

string sql = "update dbo.User_Info SET ";
if (TextFirstName.Text != null)
{
    sql += "FirstName=@FirstName, ";
    cmd.Parameters.Add("FirstName", SqlDbType.VarChar).Value = TextFirstName.Text;
}
// etc.

Change your SQL statement to check for NULL paramteres and leave the initial values if they are NULL:

// If @FirstName is NULL, "update" with the original value
cmd.CommandText = "update dbo.User_Info SET FirstName=COALESCE(@FirstName, FirstName)," 
// etc.