Without your actual data it's impossible for us to check, but I'd guess that the value in your textbox does not exactly match any of your terms: "=" in SQL requires an exact match, and an extra or missing space will cause a comparison to fail.
You could try LIKE:
... WHERE MyColumn LIKE '%' + @MyUserInput + '%' ...
as that will match "AAAAABCDDDD" and "BC" for an input of "BC" without any problems.
You also need to put the "variable" specifier in each parameter when you add it:
SqlCommand comm = new SqlCommand("Select Name, ChassisNO, CarModel, NumPlate,CarBrand,CustomsCertNum,ModelYear from dbo.FZMain where ID = @ID or ChassisNO = @ChassisNO or Name = @Name or CarModel = @CarModel or NumPlate = @NumPlate or CarBrand = @CarBrand or Cases = @Cases or CarBrand = @CarBrand or PlaceOfWork = @PlaceOfWork or PlaceOfBirth = @PlaceOfBirth or Address = @Address or Status = @Status or ModelYear = @ModelYear or cert_number = @cert_number or Payment = @Payment or CustomsCertNum = @CustomsCertNum ", conn);
comm.Parameters.AddWithValue("@ID", TextBox1.Text);
comm.Parameters.AddWithValue("@Name", TextBox1.Text);
comm.Parameters.AddWithValue("@ChassisNO", TextBox1.Text);
comm.Parameters.AddWithValue("@CarModel", TextBox1.Text);
I'd also change your query: if you are using the same input field for every comparison, then why pass it as multiple parameters? Either pass separate text boxes, or just pass the text box once:
SqlCommand comm = new SqlCommand("Select Name, ChassisNO, CarModel, NumPlate,CarBrand,CustomsCertNum,ModelYear from dbo.FZMain where ID = @ID or ChassisNO = @ChassisNO or Name = @Name or CarModel = @CarModel or NumPlate = @NumPlate or CarBrand = @CarBrand or Cases = @Cases or CarBrand = @CarBrand or PlaceOfWork = @PlaceOfWork or PlaceOfBirth = @PlaceOfBirth or Address = @Address or Status = @Status or ModelYear = @ModelYear or cert_number = @cert_number or Payment = @Payment or CustomsCertNum = @CustomsCertNum ", conn);
comm.Parameters.AddWithValue("@ID", tbID.Text);
comm.Parameters.AddWithValue("@Name", tbName.Text);
...
Or
SqlCommand comm = new SqlCommand("Select Name, ChassisNO, CarModel, NumPlate,CarBrand,CustomsCertNum,ModelYear from dbo.FZMain where ID = @SEARCH or ChassisNO = @SEARCH or Name = @SEARCH or CarModel = @SEARCH or NumPlate = @SEARCH or CarBrand = @SEARCH or Cases = @SEARCH or CarBrand = @SEARCH or PlaceOfWork = @SEARCH or PlaceOfBirth = @SEARCH or Address = @SEARCH or Status = @SEARCH or ModelYear = @SEARCH or cert_number = @SEARCH or Payment = @SEARCH or CustomsCertNum = @SEARCH", conn);
comm.Parameters.AddWithValue("@SEARCH", TextBox1.Text);