An exception of type 'System.Data.SqlClient.SqlException' occurred in System.Data.dll

Question

When I execute my code below, this error message occurs:

"An exception of type \'System.Data.SqlClient.SqlException\' occurred in System.Data.dll bu

Answer 1

I think your EmpID column is string and you forget to use ' ' in your value.

Because when you write EmpID=" + id.Text, your command looks like EmpID = 12345 instead of EmpID = '12345'

Change your SqlCommand to

SqlCommand cmd = new SqlCommand("SELECT EmpName FROM Employee WHERE EmpID='" + id.Text +"'", con);

Or as a better way you can (and should) always use parameterized queries. This kind of string concatenations are open for SQL Injection attacks.

SqlCommand cmd = new SqlCommand("SELECT EmpName FROM Employee WHERE EmpID = @id", con);
cmd.Parameters.AddWithValue("@id", id.Text);

I think your EmpID column keeps your employee id's, so it's type should some numerical type instead of character.

Answer 2

Try this

SqlCommand cmd = new SqlCommand("SELECT EmpName FROM Employee WHERE EmpID=@id", con);
cmd.Parameters.AddWithValue("id", id.Text);

Answer 3

There are some problems with your code. First I advise to use parametrized queries so you avoid SQL Injection attacks and also parameter types are discovered by framework:

var cmd = new SqlCommand("SELECT EmpName FROM Employee WHERE EmpID = @id", con);
cmd.Parameters.AddWithValue("@id", id.Text);

Second, as you are interested only in one value getting returned from the query, it is better to use ExecuteScalar:

var name = cmd.ExecuteScalar();

if (name != null)
{
   position = name.ToString();
   Response.Write("User Registration successful");
}
else
{
    Console.WriteLine("No Employee found.");
}

The last thing is to wrap SqlConnection and SqlCommand into using so any resources used by those will be disposed of:

string position;

using (SqlConnection con = new SqlConnection("server=free-pc\\FATMAH; Integrated Security=True; database=Workflow; "))
{
  con.Open();

  using (var cmd = new SqlCommand("SELECT EmpName FROM Employee WHERE EmpID = @id", con))
  {
    cmd.Parameters.AddWithValue("@id", id.Text);
  
    var name = cmd.ExecuteScalar();
  
    if (name != null)
    {
       position = name.ToString();
       Response.Write("User Registration successful");
    }
    else
    {
        Console.WriteLine("No Employee found.");
    }
  }
}

Answer 4

using (var cmd = new SqlCommand("SELECT EmpName FROM [Employee] WHERE EmpID = @id", con))

put [] around table name ;)

Answer 5

An unhandled exception of type 'System.Data.SqlClient.SqlException' occurred in System.Data.dll

    private const string strconneciton = "Data Source=.;Initial Catalog=Employees;Integrated Security=True";
    SqlConnection con = new SqlConnection(strconneciton);

    private void button1_Click(object sender, EventArgs e)
    {

        con.Open();
        SqlCommand cmd = new SqlCommand("insert into EmployeeData (Name,S/O,Address,Phone,CellNo,CNICNO,LicenseNo,LicenseDistrict,LicenseValidPhoto,ReferenceName,ReferenceContactNo) values ( '" + textName.Text + "','" + textSO.Text + "','" + textAddress.Text + "','" + textPhone.Text + "','" + textCell.Text + "','" + textCNIC.Text + "','" + textLicenseNo.Text + "','" + textLicenseDistrict.Text + "','" + textLicensePhoto.Text + "','" + textReferenceName.Text + "','" + textContact.Text + "' )", con);
        cmd.ExecuteNonQuery();
        con.Close();
    }

Answer 6

use try-catch to see real error occurred on you

 try
{
  //Your insert code here
}
catch (System.Data.SqlClient.SqlException sqlException)
{
  System.Windows.Forms.MessageBox.Show(sqlException.Message);
}