[c#] Using Alert in Response.Write Function in ASP.NET

I have database code like this

try
{
    string strConnectionString = ConfigurationManager.ConnectionStrings["SqlServerCstr"].ConnectionString;

    SqlConnection myConnection = new SqlConnection(strConnectionString);
    myConnection.Open();

    string hesap = Label1.Text;
    string musteriadi = DropDownList1.SelectedItem.Value;
    string avukat = DropDownList2.SelectedItem.Value;

    SqlCommand cmd = new SqlCommand("INSERT INTO AVUKAT VALUES (@MUSTERI, @AVUKAT, @HESAP)", myConnection);

    cmd.Parameters.AddWithValue("@HESAP", hesap);
    cmd.Parameters.AddWithValue("@MUSTERI", musteriadi);
    cmd.Parameters.AddWithValue("@AVUKAT", avukat);
    cmd.Connection = myConnection;

    SqlDataReader dr = cmd.ExecuteReader(System.Data.CommandBehavior.CloseConnection);
    Response.Redirect(Request.Url.ToString());
    myConnection.Close();
}
catch (Exception)
{
    Response.Write("<h2>ERROR</h2>");
}

It works fine but what I want, in the catch function, is to call the javascript alert function.

I've tried this

Response.Write("<script language=javascript>alert('ERROR');</script>);

But there is an error

How can I show error message in javascript alert function?

You ca also use Response.Write("alert('Error')");

You can simply write

try
 {
    //Your Logic and code
 }
 catch (Exception ex)
 {
    //Error message in  alert box
    Response.Write("<script>alert('Error :" +ex.Message+"');</script>");
 }

it will work fine

string str = "Error mEssage";
Response.Write("<script language=javascript>alert('"+str+"');</script>");

Replace:

Response.Write("<script language=javascript>alert('ERROR');</script>);

With

Response.Write("<script language=javascript>alert('ERROR');</script>");

In other words, you're missing a closing " at the end of the Response.Write statement.

It's worth mentioning that the code shown in the screenshot appears to correctly contain a closing double quote, however your best bet overall would be to use the ClientScriptManager.RegisterScriptBlock method:

var clientScript = Page.ClientScript;
clientScript.RegisterClientScriptBlock(this.GetType(), "AlertScript", "alert('ERROR')'", true);

This will take care of wrapping the script with <script> tags and writing the script into the page for you.

Concatenate the string separating the slash and the word script in this way.

Response.Write("<script language='javascript'>alert('Especifique Usuario y Contraseña');</" + "script>");

Use this....

string popupScript = "<script language=JavaScript>";
popupScript += "alert('Please enter valid Email Id');";
popupScript += "</";
popupScript += "script>";
Page.RegisterStartupScript("PopupScript", popupScript);