delete records using gridview ASP.NET

Question

I am writing to seek help in regards deleting database record using checkbox gridview controls.

I am trying to delete the records from “ViewData” using checkbox and gridview but the 'if' condition keeps failing. Any further assistance as to where I may be going wrong would be very much appreciated. Thank you very much for your time and feedback.

//Method for Deleting Record  
protected void DeleteRecord(int ID)
{
    SqlConnection con = new SqlConnection(cs);
    SqlCommand com = new SqlCommand("delete from tbl_Users where ID=@ID", con);
    com.Parameters.AddWithValue("@ID", ID);
    con.Open();
    com.ExecuteNonQuery();
    con.Close();
}

protected void btnDeleteRecord_Click(object sender, EventArgs e)
{
    foreach (GridViewRow grow in ViewDataGrid.Rows)
    {
//Searching CheckBox("chkDel") in an individual row of Grid  
CheckBox chkdel = (CheckBox)grow.FindControl("chkDel");
//If CheckBox is checked than delete the record with particular empid  
if (chkdel.Checked)
{
    int ID = Convert.ToInt32(grow.Cells[1].Text);
    DeleteRecord(ID);
}
    }
    //Displaying the Data in GridView  
    showData();
}

Error: Input string was not in the correct format in: int ID = Convert.ToInt32(grow.Cells[1].Text);

Answer 1

In following line

int ID = Convert.ToInt32(grow.Cells[1].Text);

The actual value of grow.Cells[1].Text might be containing alphabetic characters or the whitespace so you are getting this error.

Convert.ToInt32(stringVal) actually converts the specified string representation of a number to an equivalent 32-bit signed integer but the parameter should be a string that contains the number only.

Answer 2

With your select query in the line string SelectQuery = "SELECT FROM tbl_Users WHERE ID=" + ID; you are missing the values you are selecting.

You will either have to select the specific columns required are input * to select all columns. eg string SelectQuery = "SELECT * FROM tbl_Users WHERE ID=" + ID; or string SelectQuery = "SELECT column1,column3 FROM tbl_Users WHERE ID=" + ID;