C#

char quote = '"';
string str = "MessageBox.Show(" + quote + "hello" + quote + ")";

private void webBrowser1_DocumentCompleted(object sender, WebBrowserDocumentCompletedEventArgs e)
        {
            for (int i = 0; i < this.webBrowser1.Document.Images.Count; i++)
            {
                this.webBrowser1.Document.Images[i].Style = "display:none;";
            }
        }

sqlInsertCmd.Parameters.AddWithValue("@BezierCusp",val);

sqlInsertCmd.Parameters.Add("@BezierCusp", SqlDbType.whatever); // There are several overloads of this method, pick one that suits

// Note the syntax might not be exact here, I'm doing it from memory, but there are loads of examples on MSDN and elsewhere
sqlInsertCmd.Parameters["@BezierCusp"].Value = val;

Setup all parameter(s) *** Note NOT AddWithValue here, just Add. This MUST only be done once, so outside loop ***
start loop
{
  set value of parameter to next value from array *** NOTE this has to be done for each value, so inside loop ***
  execute command to add/insert record
}

  <big>sqlInsertCmd.Connection = con;</big> <=== Moved out of loop, only need to do it once, not for each iteration
  // Create all the parameters for your sqlInsertCmd HERE. If there are more parameters, create them here with Add NOT AddWithValue
  <big>SqlParameter ciParam = sqlInsertCmd.Parameters.Add("@cuspIndex", SqlDbType.Int);</big>
  <big>SqlParameter bcParam = sqlInsertCmd.Parameters.Add("@BezierCusp", SqlDbType.Int);</big> // I assume it is an int, but change it to the type you need
  //Using loop to get the all stroke.GetPoint , it will return Array(2dimension) , i want to add all values of array
  //In the Database In the parameter Bezier Cusp ,but it show me the error that"exSql = {"The variable name '@BezierCusp' has already been
  // declared. Variable names must be unique within a query batch or stored procedure."}
  for (i = 0; i <= 100; i = i + 1)
  {
    // Set the values of all parameters here
    <big>ciParam.Value = Convert.ToInt16(stroke.BezierCusps.GetValue(i));</big> // <== I have assumed this should be a different value
                                                                                       // for each row. If not remove this line and restore
                                                                                       // your declaration (above)
    <big>bcParam.Value = stroke.GetPoint(i).X;</big> <== Set the value of the parameter to the next value from the array
    con.Open();
    sqlInsertCmd.ExecuteNonQuery();  <== this stores value to database
    con.Close();
}

string.Format("{0:X5}", 16)