System.NullReferenceException: Object reference not set to an instance of an object:

Question

I am new in asp.net and working on the data grid view in asp.net.i have written the following code for inserting and updating the columns in grid view.the grid is showing the data very well,but when i am trying to edit any row in the grid then it is throwing an Exception:

System.NullReferenceException: Object reference not set to an instance of an object: in the following line:

string UpdateQuery = string.Format("UPDATE tbl_PaperRateList set rate=" + rate1.Text + " where companyId=" + company_id.Text + " and paperId=" +paper_id.Text+ "");


SqlConnection conn = new SqlConnection(WebConfigurationManager.ConnectionStrings["con"].ConnectionString);

protected void Page_Load(object sender, EventArgs e)
{
    if (!IsPostBack)
    {
        BindGridData();
    }
}

protected void gridRateList_RowEditing(object sender, GridViewEditEventArgs e)
{
    gridRateList.EditIndex = e.NewEditIndex;
    BindGridData();
}

protected void gridRateList_RowCancelingEdit(object sender, GridViewCancelEditEventArgs e)
{
    gridRateList.EditIndex = -1;
    BindGridData();
}
#endregion

#region  Binding the RateList Grid
public void BindGridData()
{

    {
        conn.Open();
        SqlCommand cmdCompanyId = new SqlCommand("Select max(companyId) from tbl_PaperRateList", conn);
        int c_id = Convert.ToInt32(cmdCompanyId.ExecuteScalar());

        using (SqlCommand comm = new SqlCommand("select p.paperId,"
           + "p.Rate,pm.PaperName from tbl_PaperRatelist p,tbl_papermaster pm where p.paperId=pm.paperId and p.companyId=" + c_id + "", conn))
        {
            SqlDataAdapter da = new SqlDataAdapter(comm);
            DataSet ds = new DataSet();
            da.Fill(ds);
            gridRateList.DataSource = ds;
            gridRateList.DataBind();
        }
    }
}
#endregion

#region    /*Updating the Row in Grid View*/
protected void gridRateList_RowUpdating(object sender, GridViewUpdateEventArgs e)
{

    string s = gridRateList.DataKeys[e.RowIndex].Value.ToString();

    Label company_id = (Label)gridRateList.Rows[e.RowIndex].FindControl("CompanyId");
    Label paper_id = (Label)gridRateList.Rows[e.RowIndex].FindControl("paperId");
    TextBox rate1 = (TextBox)gridRateList.Rows[e.RowIndex].FindControl("txtRate");
    string UpdateQuery = string.Format("UPDATE tbl_PaperRateList set rate=" + rate1.Text + " where companyId=" + company_id.Text + " and paperId=" +paper_id.Text+ "");


    gridRateList.EditIndex = -1;
    BindGridData(UpdateQuery);

}
#endregion

#region    Bind the Gridview after updating the row
private void BindGridData(string Query)
{
    string connectionstring = ConfigurationManager.ConnectionStrings["con"].ConnectionString;
    using (SqlConnection conn = new SqlConnection(connectionstring))
    {
        conn.Open();
        SqlCommand cmdCompanyId = new SqlCommand("Select max(companyId) from tbl_PaperRateList", conn);
        int cid = Convert.ToInt32(cmdCompanyId.ExecuteScalar());
        using (SqlCommand comm = new SqlCommand(Query +
                ";select p.paperId,"
+ "p.Rate,pm.PaperName from tbl_PaperRatelist p,tbl_papermaster pm where p.paperId=pm.paperId and p.companyId=" + cid + "", conn))
        {
            SqlDataAdapter da = new SqlDataAdapter(comm);
            DataSet ds = new DataSet();
            da.Fill(ds);
            gridRateList.DataSource = ds;
            gridRateList.DataBind();
        }
    }
}
#endregion
}

Did u declared globally or assigned null value to the variable..? like this string UpdateQuery=""; — Rajeshkumar Kandhasamy
– Rajeshkumar Kandhasamy, Commented Dec 27, 2011 at 5:23
possible duplicate of What is a NullReferenceException in .NET? — John Saunders
– John Saunders, Commented Dec 27, 2011 at 5:34
Also, why use string concatenation with String.Format? Use string.Format("UPDATE tbl_PaperRateList set rate={0} where companyId={1} and paperId={2}", rate1.Text, company_id.Text, paper_id.Text); — John Saunders
– John Saunders, Commented Dec 27, 2011 at 5:37

Rajeshkumar Kandhasamy · Accepted Answer · 2011-12-27 05:29:31Z

2

Did u declared globally or assigned null value to the variable..?

like this string UpdateQuery="";

Check the rate1.Text,company_id.Text ,paper_id.Text properties getting values or not.

Debug the Function BindGridData(string Query) the error happening there i think. check the parameters of that function. some parameters getting null value that's what the Exception is coming. check it out.

Hope this may helpful....

answered Dec 27, 2011 at 5:29

Rajeshkumar Kandhasamy

6,4997 gold badges61 silver badges84 bronze badges

Sign up to request clarification or add additional context in comments.

3 Comments

RP Nainwal Over a year ago

thanks sir,i hve debugged the function BindGridData(string Query) and i found that rate1.Text is getting the values but company_id.Text ,paper_id.Text are getting the null values.

Rajeshkumar Kandhasamy Over a year ago

k try to solve before here asking.Dubug each and every line for Null Exception if it is occured.It will be useful to you.

RP Nainwal Over a year ago

Thanks a lot sir i have solved the problems. i would like to join u in my facebuk account at [email protected]

PKJI · Accepted Answer · 2017-02-23 14:18:24Z

2

Did u declared globally or assigned null value to the variable..?

like this string UpdateQuery="";

Check the rate1.Text,company_id.Text ,paper_id.Text properties getting values or not.

Debug the Function BindGridData(string Query) the error happening there i think. check the parameters of that function. some parameters getting null value that's what the Exception is coming. check it out.

answered Feb 23, 2017 at 14:18

PKJI

415 bronze badges

Collectives™ on Stack Overflow

System.NullReferenceException: Object reference not set to an instance of an object:

2 Answers 2

3 Comments

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

2 Answers 2

3 Comments

Comments

Your Answer

Sign up or log in

Post as a guest

Related