How can i update app.config connectionstring Datasource value in C#?

Question

Configuration config = ConfigurationManager.OpenExeConfiguration(ConfigurationUserLevel.None);
config.ConnectionStrings.ConnectionStrings[\"MyConnectionString\",Stri         


        

Answer 1

What you actually want is:

Configuration config = 
    ConfigurationManager.OpenExeConfiguration(ConfigurationUserLevel.None);

// Because it's an EF connection string it's not a normal connection string
// so we pull it into the EntityConnectionStringBuilder instead
EntityConnectionStringBuilder efb = 
    new EntityConnectionStringBuilder(
        config.ConnectionStrings.ConnectionStrings["ERPDatabaseTables"]
            .ConnectionString);

// Then we extract the actual underlying provider connection string
SqlConnectionStringBuilder sqb = 
    new SqlConnectionStringBuilder(efb.ProviderConnectionString);

// Now we can set the datasource
sqb.DataSource = textBox1.Text;

// Pop it back into the EntityConnectionStringBuilder 
efb.ProviderConnectionString = sqb.ConnectionString;

// And update...
config.ConnectionStrings.ConnectionStrings["ERPDatabaseTables"]
    .ConnectionString = efb.ConnectionString;

config.Save(ConfigurationSaveMode.Modified, true);
ConfigurationManager.RefreshSection("connectionStrings");

This presumes:

1. Your EF connection string exists in the app's config file

2. You have a reference to System.Data.Entity