Set QueryTemplate programmatically to a Content By Search Web Part

Sometimes, it may be necessary to set the “QueryText” attribute of the Content Search Web Part Programmatically :

In order to override the QueryText attribute, you can override the BeforeSerializeToClient event :

public class CustomContentBySearchWebPart : ContentBySearchWebPart
{

    public CustomContentBySearchWebPart() { }

    protected override void OnLoad(EventArgs e)
    {
        if (this.AppManager != null)
        {
            if (this.AppManager.QueryGroups.ContainsKey(this.QueryGroupName) &&
                this.AppManager.QueryGroups[this.QueryGroupName].DataProvider != null)
            {
                this.AppManager.QueryGroups[this.QueryGroupName].DataProvider.BeforeSerializeToClient +=
                    new BeforeSerializeToClientEventHandler(EnhanceQuery);
            }
        }

        base.OnLoad(e);
    }

    /// <summary>
    /// BeforeSerializeToClientEventArgs Event: called before sending the query template to search    /// </summary>
    /// <param name="sender"></param>
    /// <param name="e"></param>
    private void EnhanceQuery(object sender, BeforeSerializeToClientEventArgs e)
    {

            try
            {
                DataProviderScriptWebPart dataProvider = sender as DataProviderScriptWebPart;
                StringBuilder qry = new StringBuilder();

                qry.Append("owstaxidMyProperty1:xyz;owstaxidMyProperty2:123;");

                dataProvider.QueryTemplate = qry.ToString(); 

            }
            catch (Exception ex)
            {
                //exception code
            } 

    }

 }

SharePoint 2013 : Set Content Search Web Part “QueryText” Attribute Programmatically
Programmatically change Content by Search queryTemplate
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SharePoint 2013 Content Search WebPart

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