How to create dynamic connection string in c# asp.net?

In this article, I will show you how to adding connection string in web config, via dynamically in asp.net c#.  You  can also change connection string in  web config configuration file.

The following function has the WebConfigurationManager, it opens the web.config file in the asp.net application. For dynamically adding connection string, you need to check for key and value field. If the connection string is not there, you need to a create new connection string otherwise it updates the value of connection string.

Desgin page:

<form id="form1" runat="server">
        <div style="border:1px solid #e1d8d8;height:350px;width:500px">
            <h2>Dynamically change/Update Connection string in asp.net </h2>
            <br />
            <asp:Button ID="btnUpdate" runat="server" Text="Upload Image" OnClick="btnUpdate_Click"  />
        </div>
    </form>

Code behind:

   protected void btnUpdate_Click(object sender, EventArgs e)
        {
            UpdateConnectionString("testconn", "admin");
        }
 
        public void UpdateConnectionString(string key, string value)
        {
            Configuration config = WebConfigurationManager.OpenWebConfiguration("~");
            if (config.ConnectionStrings.ConnectionStrings[key] == null)
            {
               config.ConnectionStrings.ConnectionStrings.Add(new ConnectionStringSettings(key,value));
            }
            else
            {
               config.ConnectionStrings.ConnectionStrings[key].ConnectionString =value;
            }
           config.Save();
            ConfigurationManager.RefreshSection("connectionStrings");
        }