我的Windows窗体中有三个Datagridviews。一个人带来了村庄的数据，点击任何一个单元格，第二个Datagridview填充了客户详细信息。在点击客户名称时，第三个Datagridview必须填充并计算客户的余额，无论信用是剩余还是提前存入，现在我面临的问题是第三个数据网格。
它特别抛出异常：对象引用设置为null。
private void dataGridView3_CellContentClick(object sender, DataGridViewCellEventArgs e)
{
double loansum1 = 0;
double emisum1 = 0;
double dd1 = 0;
double ei1 = 0;
double finalsum = 0;
foreach (DataGridViewRow drr1 in dataGridView3.Rows)
{
if (drr1.Cells[1].Selected == true)
{
string customerid = drr1.Cells[0].Value.ToString();
label1.Text = customerid;
SqlConnection setcon = new SqlConnection(ConfigurationManager.ConnectionStrings["sismanager"].ConnectionString);
using (SqlCommand getsup = new SqlCommand("SELECT Ciid, Cdate, Cparticulars, Ccr, Cdr FROM Customerbills WHERE Cid = @Cid ORDER BY Cdate DESC", setcon))
{
getsup.Parameters.AddWithValue("@Cid", customerid);
SqlDataAdapter drrr = new SqlDataAdapter(getsup);
try
{
setcon.Open();
DataTable data1 = new DataTable();
drrr.Fill(data1);
if (data1.Rows.Count > 0)
{
dataGridView1.DataSource = data1;
dataGridView1.Columns[0].HeaderText = "Bill Number";
dataGridView1.Columns[1].HeaderText = "Bill Date";
dataGridView1.Columns[2].HeaderText = "Particulars";
dataGridView1.Columns[3].HeaderText = "Credit Balance";
dataGridView1.Columns[4].HeaderText = "Cash Balance";
for (int ij = 0; ij < (dataGridView1.Rows.Count); ++ij)
{
dd1 = Double.Parse(dataGridView1.Rows[ij].Cells[3].Value.ToString());
ei1 = Double.Parse(dataGridView1.Rows[ij].Cells[4].Value.ToString());
loansum1 += dd1;
emisum1 += ei1;
}
label4.Text = (Math.Round(loansum1)).ToString();
label5.Text = (Math.Round(emisum1)).ToString();
finalsum = (emisum1 - loansum1);
if (finalsum >= 0)
{
label6.Text = "Rs. " + finalsum + " (Previous Amount Clear)";
}
else
{
label6.Text = "Rs. " + finalsum + " (Previous Amount Due)";
}
}
}
catch (SqlException exx)
{
}
finally
{
setcon.Close();
}
}
}
}
}
异常错误发生在：
dd1 = Double.Parse(dataGridView1.Rows[ij].Cells[3].Value.ToString());
Error Image below; It shows in call stack that the data is coming.
